In known manner, a turbine engine includes a combustion chamber in which air and fuel are mixed together prior to being burnt therein. The gas resulting from this combustion flows downstream from the combustion chamber and subsequently feeds a high pressure turbine and a low pressure turbine. Each turbine comprises one or more sets of stationary vanes, known as nozzles, alternating with one or more sets of moving blades, known as rotor wheels, with the blades being spaced apart circumferentially all around the rotor of the turbine.
Given the constraints, and in particular the temperature constraints that they need to withstand, nozzles are generally made by casting. In order to facilitate fabrication, a 360°-set of guide vanes such as a nozzle is subdivided into a plurality of angular sectors, each of which is cast separately in a shell mold.
Conventionally, a guide vane sector, also referred to below more simply as a “sector”, comprises a first platform and a second platform that are coaxial about a common axis and that have extending between them at least one airfoil, and that also have a fastener projecting from the first platform towards a first edge of the first platform.
Nevertheless, it has been observed that after metal has been cast into a shell mold of the kind usually used for this type of sector, metallurgical defects can occur in the sector such as shrinkage, i.e. material shrinking as a result of late cooling of pockets of liquid metal. There therefore exists a need for a novel type of shell mold that makes it possible to limit, or even avoid, the appearance of metallurgical defects in the guide vane sector.